U.S. Pat. Nos. 4,885,565, 5,638,060, 5,977,867, US2002/0075135 describe touch-operated apparatus having tactile feedback for a user when touched. In U.S. Pat. No. 4,885,565 an actuator is provided for imparting motion to the CRT when the actuator is energised to provide tactile feedback. In U.S. Pat. No. 5,638,060, a voltage is applied to a piezo-electric element which form a switch to vibrate the element to apply a reaction force to a user's finger. In U.S. Pat. No. 5,977,867, a tactile feedback unit generates a mechanical vibration sensed by the user when the touch screen is touched with a finger or a pointer. The amplitude, vibration frequency and duration of the mechanical vibrations are controlled, with the duration being long enough to be felt but short enough to terminate before the next key touch. US2002/0075135 describes the use of a second transducer to provide vibration in the form of transient to simulate a button click.
In each of the prior art documents described above, tactile feedback is provided in response to a discrete touch, of a user's finger or pointer.